active pf

Journal of Electrical and Electronics Engineering 139

Active Power Filters Under Marketing Aspect

SILAGHI Helga', SPOIAL Viorica', PURECE ABRUDAN Adriana',EAZECAS Eniko'

^University of Oradea, Department of Control Systems Engineering and Management,Faculty of Electrical Engineering and Information Technology ,

University Str. 1, 410087, Oradea, RomaniaPhone: +40 (0) 59 408-226 , E-mail: [email protected],[email protected]

Abstract - This paper presents some active power filtersand their solutions with equipment based on powerelectronics. A short marketing study concerning theshunt, hybrid and series active power filters isdescribed showing their main schemes, and principlesof operation. These active power filters are used forreduction of high harmonics in the supply current andare studied under marketing aspect.

Keywords: Active power flter, power converter,harmonics, marketing

I. INTRODUCTION

Between the different technical options available toimprove power quality, active power filters have provedto be an important alternative to compensate differentcurrent and voltage disturbances in power distributionsystems [1], [5].

There are several causes for voltage distortion,namely, non linear loads, some types of voltage sourcesand thunderstorms [1].

These problems cause instantaneous and long termeffects on electrical equipment. Some short term effectsare interferences, malfunctioning and degradation of theperformance of devices or equipments. Effects in thelong run arc, basically, overheating and premattire agingof the electric devices [1].

Power quality is defined by the most of the moreimportant international standards as the physicalcharacteristics of the electric supply provided undernormal operating conditions that do not disrupt or disturbthe customer's processes. Therefore, a power qualityproblem exists if any voltage, current or frequencydeviation results in a failure or in a bad operation ofcustomer's equipment. It is important to notice that thequality of power supply implies basically voltage qualityand supply reliability [1].

Voltage quality problems relate to any failure ofequipment due to deviations of the line voltage from itsnominal characteristics, and the supply reliability ischaracterized by its adequacy (ability to supply the load),security (ability to withstand sudden disturbances such

as system faults) and availability (focusing especially onlong interruptions) [1].

The power semiconductor converters are becomingto typical load in the distribution mains. Input circuits ofthese converters are often designed as a control or non-control rectifier, which consists of power semiconductordevices, [1] [6]. The converter is a no-linear load in themains and its current consumption is not only sinusoidal,but there are higher current harmonics, whichunfortunately influence the feed system. For reduction ofthe higher harmonics influence thefilters compoundedby inductors and capacitors are used. These devices havemany basic disadvantages, for example, they and innerline impedance are making resonance circuit with sharptuned resonances. All these undesirable properties can beremoved by using active power filters .

II. SERIES ACTIVE POWER FILTERS

The series active power filter is connected serialbetween the feed system and the non-linear load, [1]. Forthe direct current receivers, a category of commutationconverters have been developed which assure by meansof the PWM with a sinusoidal reference command, theabsorption from the supply of a sinusoidal current, inphase with voltage, [5].

Series active power filters represent commutationrectifiers, AC-DC converters with PWM command, withthe generally scheme as shown in figure 1 :

Fig. I. Series active power filter

140 Volume 6, Number 1, May 2013

The purpose is that the power factor to have the value1 and the current is to be sinusoidal and in phase withvoltage. In theoretical analysis the power losses in theconverter are neglected [3], [4].

III. SHUNT ACTIVE POWER FILTERS

Shunt active power filters are normally implementedwith pulse-width modulated voltage source inverters(PWM-VSI). In this type of applications, the PWM-VSIoperates as a current controlled voltage source.Traditionally, 2 level PWM-VSI have been used toimplement such system. However, in the past yearsmultilevel PWM voltage source inverters have beenproposed to develop active power filters for mediumvoltage applications.

Active power filters implemented with multiple VSIconnected in parallel to a dc bus but in series through atransformer or in cascade has been proposed in thetechnical literature.

The shunt active filter (figure 2) is designed to filterthe line currents and the series active filter is designed tofilter the mains voltages.

Fig.2. Shunt active power filter

It is also possible to combine both topologies toprovide both current and voltage filtering in a hybridactive power filter.

IV. HYBRID ACTIVE POWER HLTERS

Hybrid active power filter are obtained when activepower filters are used with passive filters improvingcompensation characteristics of the passive filter, andavoiding the possibility of the generation of series orparallel resonance.

A possibility to combine the compensationcharacteristics of passive and active power filters is byconnecting the active passive filter in series with thepassive one, as shown in Fig. 3. The compensationcharacteristics of the passive filter is significantlyimproved, since the active scheme generated voltageharmonic components across the terminal of the primarywindings of the series transformer, forcing currentharmonics generated by the load to circulate through thepassive filter instead of the power distribution system.

Fig.3. Hybrid active power filter

Simulated waveforms for this type of compensationare shown in figure 4.

Fig.4. Hybrid active power filter operation - Simulated results:(a) Load Current, (b) Passive filter current, (c) System Current.

(d) Passive Filter current, (e) System currentBy controlling the amplitude of the voltage

fundamental component across the coupling transformer,the power factor of the power distribution system can beadjusted.

Journal of Electrical and Electronics Engineering 141

The control of the load power factor imposed ahigher voltage across the filter capacitor. Thisconsideration has to be considered when the filtercapacitor is specified.

This type of configuration is very convenient forcompensation of high power medium voltage non linearloads, such as large power ac drives withcycloconverters or high power medium voltage rectifiersfor application in electrowining process or forcompensation of arc furnace. In all these applicationspassive filters alone do not have enough compensationcapability to reduce current harmonics.

In the previous figures simulated results shown in (a),(b) and (c) correspond to the operation without the seriesactive power filter. In this case the total harmonicdistortion of the system current is 11.3 %, proving thatthe passive filter can not compensate all the currentharmonics. In figures (d) and (e) the series active powerfilter is operating. Eigure (e) shows that the THD of thesystem current is reduced to 2.1 %.

V. MARKETING ASPECT OE ACTIVE POWERHLTER STUDY

Different electrical companies are offering powerlihe conditioner or active power filter equipment tocompensate power quality problems. Based on state ofthe art power electronic technology, they have developeddifferent systems to compensates not only currentharmonic, but also fiicker compensation and voltageregulation [10].

Siemens, ABB, Hitachi, Euji and many othercompanies are offering power line conditioners toimprove power quality. These power line conditionersare based in shunt active power filter and series activepower filter topologies. Specially Siemens has developedboth approaches as well as ABB.

ABB has also been developing active power filters toimprove voltage regulation and unbalances in powersystems. The approach developed by ABB is based inboth shunt and series active power filters implementedwith IGCT based voltage source PWM inverters [10].

Currently active power line conditioner are typicallybased on IGBT or GTO thyristors voltage source PWMconverters and connected to low and medium voltagedistribution systems in shunt, series or both at the sametime. In comparison to conventional passive LC filters,active power filters offer very fast control response andmore fiexibility in defining the required control tasks fora particular application. Some of the active power filtersavailable in the market and in use to compensate powerdisturbance problems are described below [10].

The selection of equipment for improvement ofpower quality depends on the source of the problem. Incase of the Siemens Power Conditioner (SIPCON),which is based on standard IGBT drive-converters, theseries-connected Power Conditioner, also calledDynamic Voltage Regulator, (DVR) is most preferableto protect the consumer from supply voltagedisturbances. However, if the objective is to reduce the

network perturbations due to distorted load currents theshunt-connection (also called DSTATCOM), is moreappropriate.

Many shunt active filter consisting of PWM invertersusing IGBTs or GTO thyristors have been operating inJapan, with a rating capacity which ranges from 10 kVAto several MVA. Euji Electric has developed andintroduced in the market shunt active power filters withrated power between 50 and 400 kVA for low voltageapplication. Toshiba has developed a shunt active powerfilter based on three voltage fed PWM inverters usingGTO thyristors, each of which is rated at 16 MVA, for aspecific application [10].

The three active power filters are used to compensatethe fiuctuating reactive current and negative sequencecurrent component generated by the Japanese "bullet"trains. In this case, the purpose of the shunt active powerfilters with a total rating power of 48 MVA is tocompensate for voltage regulation, voltage variation andunbalance at the terminals of the 154 kV power systemto improve the power quality. In this particularapplication, the active filters are effective incompensating not only voltage regulation, but also inreducing the voltage unbalance from 3.6 % to 1 %.CEGELEC has developed shunt active power filtersbased on GTO voltage source inverters. The use of suchsystem developed by Cegelec in collaboration withElectricit de Erance (EDE's) R&D Group, is to controlinterference in the Paris mass transit authority network,which was caused by the 15 Kv busbar. In this case, byusing a GTO active power filter, the general harmonicdistortion in the current was reduced from 5.8 % to 2 %.

Another Japanese company named Meiden, hasdeveloped the Multi-Eunctional Active Eilter, also basedon voltage-fed PWM IGBTs inverters. This is a shuntactive power filter designed to compensate currentharmonics, power factor and voltage regulation. Currentharmonic compensation is possible from the secondcomponent to the 25th. The rated power of the differentmodels range between 50 to 1000 kVA. The standardspecifications of these active power filters are thefollowings:

Number of phases: 3-phase and three wires.Input voltage: 200, 210, 220 10%, 400, 420, 440 10%, 6600 10%. Frequency: 50/60 Hz 5 %. Numbers of restraint harmonic orders: 2 to 25 th. Harmonic restraint factor: 85 % or more at the ratedoutput. Type of rating: continuous. Response: 1 ms or less.

Harmonic currents fiowing on the source side whenno measure are taken for harmonic suppression, and IH2are the harmonic currents flowing on the source sidewhen harmonics are suppressed using an active filter.Current Technology Inc. has developed the HarmonixHX3-100 a shunt active power filter designed tocompensate triple harmonics generated by single-phase

142 Volume 6, Number 1, May 2013

non linear loads These zero sequence currentcomponents flow through the neutral conductor of thepower distribution system. This equipment is able tocancel up to 100 A of zero-sequence harmonics from athree-phase four-wire distribution system [10].

Technical reports show that the cancellationeffectiveness of this active power filter is equal to 94.4%, that means that the active power filter is able toreduce the neutral current from 99.1 A to 6.82 A.

Mitsubishi Electric developed the MELACT-1100Series of three-phase active power filters with ratedpower from 50 to 400 kVA in for three-phase applicationin 220, 440, and 6600 Volts. The absorption capabilitiesof harmonics is up to the 25 th order. Between 1986 and1993, Mitsubishi reports the construction andimplementation of more 100 active power filters inJapan, with rated power below 1000 kVA, forapplication in low and medium voltage. Also, Mitsubishideveloped the Compact Statcom, similar to asynchronous condenser, that provides reactive powercompensation to solve a variety of power system andindustrial system voltage fluctuations and stabilitycondition^ The Statcom consists of a self-controlled dcvoltage source, and self commutated inverters usingGTO thyristors. Mitsubishi Electric developed theworlds first static compensator in 1991 rated 154 kV and80 MV^. It was installed on an actual power system atthe Intiyamaswitching substation of the Kansai ElectricPower Co. in Japan and continues to operate today ABBhas also been developing active power filters to improvevoltage regulation and unbalances in power systems. Theapproach developed by ABB is based in both shunt andseries active power filters implemented with IGCT basedvoltage source PWM inverters [10].

The series active power filter is designed for voltagecompensation, while the shunt approach is more orientedto current compensation. The series active power filter iscalled Dynamic Voltage Regulator (DVR), while theshunt scheme is named Distribution Static SynchronousCompensator (DSTATCOM) and both equipment aredesign to compensate reactive power, in order toimprove voltage regulation. The DSTATCOM can alsooperate in conjunction with a solid state circuit breaker(SSCB) and with a Battery Energy Storage System(BESS). In this case this scheme operates as a highpower UPS, compensating outage of voltage.

VI.CONCLUSIONS

This paper presents some power quality problems indistribution systems and their solutions with powerelectronics based equipment. Shunt, hybrid and series

active power filters are described showing theircompensation characteristics and principles of operation.These active power filters are used for reduction of highharmonics in the supply current and are studied undermarketing aspect. If the mains voltage is undistorted, butnon linear loads are connected to the electrical grid, thecurrent harmonics produced will cause voltagedistortions in the line impedances, and the voltage at theload terminals will also be distorted. With a distortedvoltage, even linear loads absorb distorted currents.

By summarizing of all reached results, the hysteresiscurrent value control presents the following advantegesin comparison with the borderline control: a comparisonof the current's panta is not necessary and if the ripple issmall, the current is approximate by a sinusoid.

The shunt active filter is designed to filter the linecurrents and the series active filter is designed to filterthe mains voltages.

In this paper the use and advantages of applyingactive power filters to compensation power distributionsystems has been presented.

The principles of operation of shunt series and hybridactive power filters have been presented. Also, a briefdescription of the state of the art in the marketing ofactive power filter study has been described.

REFERENCES

[I] S. Hussain, K. Satyanaraiana, B.K.V. Prasad, "Power QualityImprovement by Using Active Power Filters", IntemationalJournal of Engineering Science and Advanced Technology, Cluj-Napoca, ISSN 2250-3676, pp. 1-7, 2012

[2] H. Silaghi, T. Loman, "Errors in Electromagnetic TorqueDetermination for a Two-Phase Asynchronous Motor," inScientific Bulletin of Electrical Engineering Faculty, No. 2, pp.47-49. 2008.

[3] M.O. Popescu, S.N. Manias, CL. Popescu, "Static Converterswith forced Commutation", ICPE Publishing, Bucharest, 1997.

[4] I. Boldea, C. Wang and S. A. Nasar, "Design of a three-plmseflux reversal machine", EMPS, vol. 27, pp. 849-863, 1999.

[5] H. Silaghi, " Energy quality in electrical drive systems withinduction machine", TREIRA Publishing, Oradea, 2000.

[6] J. Thunes, R. Kerman, D. Schlegel and T. Rowan, "CurrentRegulator Instabilities on Parallel Voltage-Source Inverters",IEEE Transactions on Industry Applications, Vol. 35, No], pp.70-78, 1999.

[7] T. H. Barton, "Rectifiers, cycloconverters and AC Controllers",Clarendon Press, Oxford, 1994.

[8] I. Boldea, S. A. Nasar, "Vector control of AC drives", CRC Pre.ss,London, 1992).

[9] R. Crowder, "Electric drives and their controls", Oxford SciencePublications, 1995.

[10] L.A. Moran, J,W. Dixon, J.R. Espinoza, R. Wallace " UsingActive Power Eilters to Improve Power Quality", Robotica(2001), pp. 11-19, Cambridge University Press, 2001.

[II] S. E. Rauch and L. J. Johnson, "Design principles of flux-switching alternators," AIEE Trans. Vol. 74III, pp. 1261-1268,1955.

Copyright of Journal of Electrical & Electronics Engineering is the property of Journal ofElectrical & Electronics Engineering and its content may not be copied or emailed to multiplesites or posted to a listserv without the copyright holder's express written permission.However, users may print, download, or email articles for individual use.